1. Field of the Invention
The present invention relates to an automatic measuring system of the viscosity of a liquid; and, more particularly, to an apparatus for automatically measuring the viscosity of a liquid, including an automatic control system which can inject a sample liquid into and discharge same from a plurality of viscosimeter tubes.
2. Description of the Prior Art
As is well known in the art, a capillary viscosimeter tube or a vacuum viscosimeter tube is generally used to measure certain lesser viscous liquids. In accordance with the known method of employing viscosimeter tubes, measurement of liquid viscosity is carried out by following the steps of: injecting manually a given volume of sample liquid into a vertical or inclined capillary tube; maintaining the volume of liquid in the tube at a predetermined temperature; measuring the passage time of the volume of liquid between two points of the tube; computing the relative viscosity of the liquid by comparing the passage time of the sample liquid with that of a reference liquid measured under the same condition; and obtaining the absolute and the intrinsic viscosities of the sample liquid based on the measured relative viscosity of the sample and the viscosity of the reference liquid. However, in such typical method of measuring the viscosity of a liquid, the procedure is rather cumbersome due to, e.g., manual introduction of the sample into the tubes and the like.
In addition, there have been provided various viscosimeters for measuring liquid viscosity as known in the art. For example, disclosed in U.S. Pat. No. 3,604,247 is an automatic viscosimeter which comprises a measurement tube, a jacket for containing a transparent liquid therein and maintaining the tube at a constant temperature, means for filling the tube with a sample liquid to be measured, and means for measuring the passage time of the sample between two points.
U.S. Pat. No. 3,713,328 to Choji Aritomi teaches an apparatus for measuring the viscosity of opaque liquids as well as transparent ones, which comprises a viscosimeter having a timing bulb, means for measuring the flow time of the liquid through the timing bulb, means for evacuating the liquid out of the viscosimeter, and means for washing and drying the viscosimeter.
Such viscosimeters as disclosed in the above patents have the disadvantages in that they cannot measure the viscosity of a number of sample liquids at the same time. Further, extra care is required in injecting a sample liquid into the conventional viscosimeter because the liquid is manually supplied to the viscosimeter.
Disclosed in U.S. Pat. No. 3,908,411 is a device for detecting the level of a liquid in a transparent tube, which is suitable for use in capillary tube type viscosimeters.
In U.S. Pat. No. 3,798,966, there is provided a single viscosimeter tube having capillaries of different sizes, which can measure viscosity over a wide range. The measurement task as disclosed in this patent is carried out by a large number of processes; and, therefore, requires a laborious and skillful work. Furthermore, the manufacturing cost of the apparatus is relatively high as it is made in rather complicated structures.